Causality in curved space

Aljasem Alashour, Bassem
The notion of Causality is a key concept in formulating theories that describe real physical systems. So when a proposed model violates this concept this usually signals the existence of an error in the conceptual formulation or in the physical understanding of the results, which might indicate to us which models should we pursue, modify or drop all together. In this work the possibility of causality violations introduced by modifying Einstein gravity is studied using the idea of the time-delay introduced to a particle while crossing the shock-wave generated by another particle, known as Shapiro-like time delay. We will see that some of the apparent causality violations are just a mathematical artifact of our formulations. While in other cases these violations can be lifted off if the theory is embedded in another theory with a better behaved UV completion. Is it also noticed that when we study local causality in (2+1) General Relativity the notions of causality and unitarity are compatible with each other.


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Yakaboylu, Enderalp; İpekoğlu, Yusuf; Department of Physics (2010)
In this thesis, entanglement under fully relativistic settings are discussed. The thesis starts with a brief review of the relativistic quantum mechanics. In order to describe the effects of Lorentz transformations on the entangled states, quantum mechanics and special relativity are merged by construction of the unitary irreducible representations of Poincaré group on the infinite dimensional Hilbert space of state vectors. In this framework, the issue of finding the unitary irreducible representations of ...
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Edelstein, Jose D.; Giribet, Gaston; Gomez, Carolina; Kilicarslan, Ercan; Leoni, Matias; Tekin, Bayram (2017-05-12)
We study the constraints coming from the local causality requirement in various 2 + 1 dimensional dynamical theories of gravity. In topologically massive gravity, with a single parity noninvariant massive degree of freedom, and in new massive gravity, with two massive spin-2 degrees of freedom, causality and unitarity are compatible with each other and both require the Newton's constant to be negative. In their extensions, such as the Born-Infeld gravity and the minimal massive gravity the situation is simi...
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Dağ, Hüseyin; Zeyrek, Mehmet Tevfik; Department of Physics (2010)
Quantum Chromodynamics(QCD) is part of the Standard Model(SM) that describes the interaction of fundamental particles. In QCD, due to the fact that strong coupling constant is large at low energies, perturbative approaches do not work. For this reason, non-perturbative approaches have to be used for studying the properties of hadrons. Among several non-perturbative approaches, QCD sum rules is one of the reliable methods which is applied to understand the properties of hadrons and their interactions.\ In th...
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Uyanık, Kıvanç; İpekoğlu, Yusuf; Department of Physics (2008)
Being a puzzling feature of quantum mechanics, entanglement caused many debates since the infancy days of quantum theory. But it is the last two decades that it has started to be seen as a resource for physical tasks which are not possible or extremely infeasible to be done classically. Popular examples are quantum cryptography - secure communication based on laws of physics - and quantum computation - an exponential speedup for factoring large integers. On the other hand, with current technological restric...
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Kavuk, Mehmet; Sarıoğlu, Bahtiyar Özgür; Department of Physics (2005)
In this thesis properties of the Gödel spacetime are analyzed and it is explicitly shown that there exist closed timelike curves in this spacetime. Geodesic motions for massive particles and light rays are investigated. One observes the focusing effect as a result of the solution of the geodesic equations. The time it takes for a free particle released from a point to come back to its starting point is calculated. A geometrical interpretation of the Gödel spacetime is given and the question of what the Göde...
Citation Formats
B. Aljasem Alashour, “Causality in curved space,” M.S. - Master of Science, Middle East Technical University, 2018.